This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The ultimate inability of the immune system to eliminate cytomegalovirus (CMV) from the host is likely due to sophisticated viral evasion mechanisms that target many aspects of the host immune system. In this project, we will try to gain a better understanding of the molecular mechanisms by which CMV modulates the induction of innate immune responses, particularly the interferon response. Specific aim 1 is to identify how HCMV activates interferon-regulatory factor 3 (IRF3). This aim has been completed and the results have been published. Specific Aims 2 and 3: are to determine how human and rhesus CMV interfere with IRF3-dependent transcriptional induction of interferon-stimulated genes (ISGs). We have tested our original hypothesis that the tegument proteins pp65 and pp71 are responsible for inhibiting IRF3 activation by RhCMV by generating deletion viruses. However, since these viruses still inhibit IRF3 activation, we now hypothesize that RhCMV contains additional IRF3 inhibitory genes. Current experiments are aimed at identifying these genes. In addition, we now explore the inhibition of IFN-dependent ISG induction by RhCMV and we have generated evidence that HCMV also inhibits IRF3 activation. In a competitive supplement to this application, we will examine whether RhCMV lacking pp65 and pp71 is capable of primary and re-infection in rhesus macaques. This is a new grant, but represents a competitive supplement to parent grant (RO1 AI070890) to study the role of RhCMV pp65 in vivo.